The Na,K-ATPase is an important membrane-associated enzyme responsible for maintaining the high internal potassium concentration and low internal sodium concentration characteristic of most animal cells. In the kidney the ion gradients created by the Na,K-ATPase are fundamental to water and Na reabsorption, the cotransport of amino acids, sugars and phosphate, and the countertransport of protons. Changes in renal Na,K-ATPase activity have been implicated in the chronic adaptation of the kidney to alterations in Na reabsorptive or K secretory load, the renal hypertrophy associated with diabetes, and tubular cyst formation found in polycystic kidney disease. Although Na,K-ATPase activity is regulated in a tissue specific and developmental fashion, little is known concerning Na,K-ATPase expression in the developing kidney. To study the development of renal Na,K-ATPase, the genes coding for the alpha, alpha isoforms, beta and gamma subunits will be used to characterize Na,K-ATPase mRNA in metanephroi, neonatal, juvenile and adult renal tissue. Isoform specific antibodies will be used to characterize Na,K-ATPase alpha isoform expression in the developing kidney. These results will be correlated to the levels of polypeptide expression of the beta and gamma subunits. To better understand the regulation of Na,K-ATPase activity in the developing kidney, the levels of mRNA and protein will be compared to the Na,K-ATPase activity. The role of the Na,K-ATPase subunits in the development of renal function will be determined by specifically blocking subunit expression with antisense oligodeoxyribonucleotides. In this manner the roles of the individual subunits in kidney development can be determined. In addition, to establish if growth factors produced by the metanephroi and developing kidney regulate Na,K-ATPase expression, Na,K-ATPase activity will be characterized in metanephroi grown in the presence of growth factor antibodies or antisense oligodeoxyribonucleotides. These studies will be important in defining the role of growth factors in metanephrogenesis. In the kidney relatively little is known about the changes in the expression of the individual Na,K-ATPase subunits during development. this characterization may be important in identifying changes in Na,K-ATPase expression and function associated with renal development and may provide clues to the role of the Na,K-ATPase during the nephropathy associated with several diseased states.